1. Field of the Invention
The present invention relates to a method and a device for manufacturing an elastic abrasive, a method and device for blasting, more specifically, relates to a method for manufacturing an elastic abrasive having a structure that abrasive grains are attached to a surface of an elastic core and a device for carrying out the method, and a method and device for circulation-type blasting structurally including the method or the device for manufacturing the elastic abrasive as a method or device for recycling the elastic abrasive.
Note that the “manufacture” of the elastic abrasive in the present invention includes attachment of the abrasive grains to the surface of the unused core, as well as “recycle” by (re)attaching the abrasive grains to the surface of the core of the elastic abrasive on which the abrasive grains are removed from the surface by use (including the core on which abrasive grains are remained).
2. Description of the Related Art
Various elastic abrasives having cores which carry abrasive grains e.g. by kneading the abrasive grains into elastic cores or attaching the abrasive grains to the surfaces of the elastic cores have been proposed (Japanese Patent No. 2,957,492, Japanese Patent Laid-Open No. 2001-207160, Japanese Utility Model Laid-Open No. S55-98565), and a shock caused by collision with a workpiece is absorbed due to elasticity of the core by blasting using this elastic abrasive. As a result, a satin finished surface formed on the surface of the workpiece caused by general blasting is reduced while processings such as polishing, removal of an oxide film and deburring are enabled for the workpiece.
Particularly, in an elastic abrasive using a core suppressing impact resilience for preventing recoiling in collision, mirror finishing which was impossible in the conventional blasting can also be carried out by sliding an ejected elastic abrasive on a surface of the workpiece, which considerably contributes to widen uses of the blasting (Japanese Patent Laid-Open No. 2006-159402).
A structure of such an elastic abrasive may include a structure that abrasive grains are kneaded into a core composed of an elastic material such as a rubber to make the core to carry the abrasive grains (see UM '8565), and structures that abrasive grains are attached to a surface of a core such as a structure that a plant fiber having adhesiveness in its oil and sugar contents is used as a core (Pat '7492) or a structure that a gelatin which exerts adhesiveness and elasticity depending on water content is used as a core ('7160).
Particularly, for manufacture of the elastic abrasive having the structure that the abrasive grains are attached to the surface of the core, the core was introduced into a rotating drum together with abrasive grains and stirred as it is in a case of a core exerting self-adhesiveness such as a plant fiber having adhesiveness in its oil and sugar contents and gelatin as mentioned above, or through coating of the core with an adhesive or an agglutinant in a case using a resin such as polyurethane without self-adhesiveness as a core, so that the abrasive grains are contacted then firmly and densely attached to the surface of the core by colliding, rubbing and pressing the core contacted with the abrasive grains to the inner wall of the drum and other cores by centrifugation. This method is also used for recycling the elastic abrasive with surface from which the abrasive grains were fallen off by use.
In the case that the elastic abrasive including a core which exerts adhesiveness and elasticity by containing water is used among the above-mentioned elastic abrasives, in light of change of the processed state according to the change of the elasticity and adhesiveness of the core by drying with time, it is also proposed that, in a circulation-type blasting device which recovers an abrasive once ejected and re-ejects it, the water content of the elastic abrasive can be adjusted by providing a liquid supplying means which sprays water in a circulation system of the elastic abrasive (Japanese Patent Laid-Open No. 2009-125818).
In the case that blasting is carried out by using the elastic abrasive having a structure that abrasive grains are attached to a surface of the core among the elastic abrasives described as related art, the abrasive grains attached to the surface of the core of the elastic abrasive are fallen off by impact and friction in collision, and the amount of the abrasive grains attached to the surface of the core is decreased as the number of the collision with the workpiece increases.
Hence, in the case that blasting using an elastic abrasive is carried out in a circulation-type blasting device, cutting performance of the elastic abrasive gradually decreases with time as shown in FIG. 10, and there is a large difference in states of the surfaces such as gloss and specularity between a processed state of a workpiece processed by the new elastic abrasive and a processed state of a workpiece processed by using the elastic abrasive repeatedly used.
Even if the elastic abrasive is exchanged for new abrasive at regular intervals in order to prevent the change of the processed state, the cutting amount is temporarily increased immediately after the exchange, however the cutting amount is decreased with time, the cutting amount unstably changes as shown in FIG. 10, and therefore the workpiece still cannot be processed with a certain level of quality.
Thereby, in the case that blasting is carried out by using an elastic abrasive having a structure that abrasive grains are attached to a surface of the core, it is necessary to use batch processing by exchanging the elastic abrasive at each time of use or exchange for a new elastic abrasive in a short period after recycling several times. Therefore, there is a problem that the productivity is considerably decreased because the blasting is interrupted by each exchange.
As presented in '5818, in order to uniform the processed state in blasting using the elastic abrasive comprising the core having elasticity and adhesiveness which is changed according to change of water content, it is proposed to prevent change of the processed state accompanying dry of the elastic abrasive even in a case of recycling use of the elastic abrasive by providing a liquid supplying unit which sprays water into the circulation system of the abrasive in the circulation-type blasting device. Also in relation to the abrasive grains fallen off from the surface of the core, if the elastic abrasive can be similarly recycled in the circulation system of the abrasive, the blasting can be continuously carried out without interrupting the processing.
However, the elastic abrasive with the core from which the abrasive grains are fallen off is recycled by introducing the elastic abrasive to be recycled into the drum together with the abrasive grains and stirring as mentioned above then densely and firmly attaching the abrasive grains not only by attaching new abrasive grains to the core exposed by which the abrasive grains are fallen off, but also by pressing and fixing the new abrasive grains to the surface of the core by giving collision, friction and centrifugal force generated in stirring. Consequently, it is impossible to recycle an elastic abrasive simply by spraying water to the elastic abrasive circulating in the blasting device.
On the other hand, since the above-mentioned drum-shaped manufacturing device for elastic abrasive is large in size, the structure of the device is getting larger in a case that this device is combined with a circulation-type blasting device. Furthermore, since the recycle of the elastic abrasive in the drum-shaped manufacturing device is carried out in the batch style, even if the manufacturing device is combined with the circulation-type blasting device, the blasting device must be eventually stopped for recycling the elastic abrasive.
The present invention has been made to solve the problems in the related art described above, and an object thereof is to provide a method and a device for manufacturing an elastic abrasive having a core to which abrasive grains are densely and firmly attached like the above-mentioned drum-shaped device for manufacturing the elastic abrasive, while enabling the device to be downsized and to continuously manufacture the elastic abrasive, thus enabling to incorporate the process and/or device for recycling the elastic abrasive in the device for circulation-type blasting or the process using the device for circulation-type blasting, thereby the workpiece can be continuously processed for the long time while maintaining the processed state of the workpiece constant in the blasting using the elastic abrasive.